Evidence based management of hypertension: What to do when blood pressure is difficult to control

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Abstract
Assessing cause and incidence of resistant blood pressure The categories of causes of resistant hypertension are Inaccurate blood pressure measurement White coat hypertension Disease progression suboptimal treatment Non-compliance with prescribed treatments Antagonising substances Coexisting conditions Measurements of blood pressure taken in the patient's home can be combined with those obtained in the doctor's office to create a fuller picture of blood pressure control Secondary hypertension. Two or more of these categories may be relevant in one patient. There is little evidence as to how often these eight categories are found to be responsible for difficulty in controlling blood pressure, but a small descriptive survey from a referral clinic gave the following relative proportions: suboptimal treatment, 40%; non-adherence to prescribed treatment, 10% to 50%; white coat hypertension, 2% to 4%; and secondary causes, 10%.5 The figures could be quite different in primary care, with lower rates of secondary causes, but there is little direct evidence on the point. Inaccurate blood pressure measurement The accuracy of blood pressure readings depends on the use of proper technique and on the conditions under which the measurements are made. Before you conclude that a patient has resistant hypertension, blood pressure measurements should be repeated under good conditions and with as near to ideal technique as possible. White coat hypertension Some patients have acceptably controlled blood pressure while they are at home but have higher readings when examined by the clinician, who may be misled to think that the patient's blood pressure is poorly controlled. To exclude this possibility, arrange for multiple measurements of the patient's blood pressure by, for example, visits to or from nurses or other healthcare workers, self monitoring with a home sphygmomanometer, or ambulatory blood pressure monitoring. If good technique is used with well calibrated equipment, these measurements can be combined with those in the doctor's office to create a fuller picture of blood pressure control. If these external readings are also persistently raised, one can conclude that the blood pressure is not yet satisfactorily controlled. Disease progression With time, the blood pressure in adults with hypertension will gradually increase.6 There is no recent, rigorous evidence as to how often disease progression is the sole cause of resistant hypertension, but without firm evidence to the contrary it seems unwise to accept it as such until other causes have been excluded. suboptimal treatment The regimens prescribed for patients may not be optimally individualised for many reasons. Many patients require aggressive treatment with several drugs to achieve target blood pressure levels. To detect suboptimal treatment, review all the drugs a patient is taking, as well as the patient's dietary habits and exercise pattern. Consider whether the dosage of each drug prescribed conforms in all respects with recommendations for its rational use and with what is known about the patient's unique health status and preferences. Hypervolaemia resulting from a high intake of dietary sodium frequently plays an important part in resistant hypertension, and better use of diuretics is often the answer when a patient's blood pressure is difficult to control.7–9 Clinicians should review regimens regularly to see if the patients' treatment plans are optimal. Antagonists that can increase blood pressure Adrenal steroids (especially mineralocorticoids) Alcohol Amphetamines—for example, appetite suppressants Anaesthetics, local and general Antidiuretic hormone and angiotensin Caffeine Cocaine Cyclosporin Disulfiram Erythropoietin Licorice and carbenoxolone Monoamine oxidase inhibitors, combined with foods containing tyramine or with amphetamine Medications containing sodium—for example, antacids or parenteral antibiotics Non-steroidal anti-inflammatory drugs Oral contraceptives Sympathomimetic agents—for example, nasal decongestants or bronchodilators Withdrawal of antihypertensive agents—for example, β blockers or clonidine Non-compliance No matter what treatments are prescribed, they will have no effect if drugs are not taken. For any number of reasons, patients may not take their drugs as prescribed or may not take them at all. Direct and non-judgmental questioning at routine clinic visits is the best way of detecting non-compliance. A systematic review of the discriminatory power of such simple questioning estimated its sensitivity to be 55% and its specificity to be 87%.10 Antagonising substances Patients may be taking many prescription and non-prescription drugs and dietary and other substances that can increase blood pressure or oppose the actions of antihypertensive drugs (see box). No rigorous studies have evaluated the frequency or magnitude of effects of such substances on blood pressure. Non-steroidal anti-inflammatory drugs (NSAIDs) account for 5% to 10% of all prescriptions in developed countries. 11 12 If they do raise blood pressure or oppose the effects of antihypertensive drugs, then they could, because of the extent to which they are taken, have a considerable impact on blood pressure control. View larger version: In this window In a new window A commonsense approach to evaluating resistant hypertension Two systematic reviews have examined the effect of non-steroidal anti-inflammatory drugs on blood pressure. One summary of findings from 54 trials found that treatment with non-steroidal anti-inflammatory drugs increased mean arterial blood pressure by 1.1 mm Hg in normotensive patients and by 3.3 mm Hg in patients with hypertension.13 Most of these trials were short (less than six weeks), and none included elderly patients. Among the non-steroidal anti-inflammatory drugs, indometacin had the largest effect on blood pressure and aspirin the least. Another systematic review summarised...